[Mlir-commits] [mlir] [MLIR][NVGPU] Add convert.fpext and convert.fptrunc Ops (PR #199700)

[Durgadoss R]

================
@@ -1709,6 +1711,669 @@ struct NVGPURcpOpLowering : public ConvertOpToLLVMPattern<nvgpu::RcpOp> {
         rewriter);
   }
 };
+
+//===----------------------------------------------------------------------===//
+// FPTruncOp Lowering
+//===----------------------------------------------------------------------===//
+
+/// Conversion op identifier for nvgpu.convert.fptrunc lowering dispatch table.
+enum class TruncConvOp {
+  F32x2_TO_F16x2,
+  F32x2_TO_BF16x2,
+  F32x2_TO_F8x2,
+  F32x2_TO_F6x2,
+  F32x2_TO_F4x2,
+  F16x2_TO_F8x2,
+  F16x2_TO_F4x2,
+  BF16x2_TO_F8x2,
+  BF16x2_TO_F4x2,
+};
+
+enum class TruncSrcKind { F32, F16, BF16 };
+
+enum class TruncDstKind { F16, BF16, F8, F6, F4 };
+
+struct TruncTableEntry {
+  TruncSrcKind src;
+  TruncDstKind dst;
+  TruncConvOp convOp;
+  int srcStepDecrement; // 2 for f32 pairs, 1 for f16x2/bf16x2
+};
+
+static constexpr TruncTableEntry kTruncTable[] = {
+    // f32 source
+    {TruncSrcKind::F32, TruncDstKind::F16, TruncConvOp::F32x2_TO_F16x2, 2},
+    {TruncSrcKind::F32, TruncDstKind::BF16, TruncConvOp::F32x2_TO_BF16x2, 2},
+    {TruncSrcKind::F32, TruncDstKind::F8, TruncConvOp::F32x2_TO_F8x2, 2},
+    {TruncSrcKind::F32, TruncDstKind::F6, TruncConvOp::F32x2_TO_F6x2, 2},
+    {TruncSrcKind::F32, TruncDstKind::F4, TruncConvOp::F32x2_TO_F4x2, 2},
+    // f16 source
+    {TruncSrcKind::F16, TruncDstKind::F8, TruncConvOp::F16x2_TO_F8x2, 1},
+    {TruncSrcKind::F16, TruncDstKind::F4, TruncConvOp::F16x2_TO_F4x2, 1},
+    // bf16 source
+    {TruncSrcKind::BF16, TruncDstKind::F8, TruncConvOp::BF16x2_TO_F8x2, 1},
+    {TruncSrcKind::BF16, TruncDstKind::F4, TruncConvOp::BF16x2_TO_F4x2, 1},
+};
+
+static bool isConvertibleF8Type(Type t) {
+  return isa<Float8E4M3FNType, Float8E5M2Type, Float8E8M0FNUType>(t);
+}
+
+static std::optional<TruncSrcKind> classifySrcType(Type t) {
+  if (t.isF32())
+    return TruncSrcKind::F32;
+  if (t.isF16())
+    return TruncSrcKind::F16;
+  if (t.isBF16())
+    return TruncSrcKind::BF16;
+  return std::nullopt;
+}
+
+static std::optional<TruncDstKind> classifyDstType(Type t) {
+  if (t.isF16())
+    return TruncDstKind::F16;
+  if (t.isBF16())
+    return TruncDstKind::BF16;
+  if (isConvertibleF8Type(t))
+    return TruncDstKind::F8;
+  int bitWidth = t.getIntOrFloatBitWidth();
+  if (isa<IntegerType>(t) && bitWidth == 8)
+    return TruncDstKind::F6;
+  if (bitWidth == 4)
----------------
durga4github wrote:

could you please help me understand why we dont need `isa<IntType>` check here?

https://github.com/llvm/llvm-project/pull/199700